A rack system (a system) managing a plurality of servers installed in one rack is known. In recent years, the number of servers which can be installed in one rack has been increasing with server densification.
Regarding such a rack system, in view of the cooling efficiency of servers and a power supply facility within a rack, the upper limit of electric energy which can be used by one rack may be set (for example, see Patent Document 1).    Patent Document 1: Japanese Unexamined Patent Application Publication No. JP-A 2009-118728
A server can operate as a specific function such as a web server, a mail server, an application server and a database server. For example, a server is equipped with a plurality of operating systems (OS) which run the respective functions, and the server changes and initiates the OS, thereby realizing operation as a specific function. With such a configuration, a plurality of servers installed in one rack or a plurality of racks do not always operate as the same function, and may operate as different functions. Consequently, load and power consumption vary among servers in one rack depending on a time. Moreover, load and power consumption vary among racks depending on a time. Thus, a problem of increase of heat generation and power consumption in the entire rack and also a problem of inability to efficiently use resources occur. As a result, a problem of instability of the operation status and performance degradation occurs.